Monazite grains from Greater Himalayan Sequence gneisses, Langtang valley, Nepal, were chemically mapped and then dated in situ via Th-Pb ion-microprobe analysis. Correlation of ages and chemistry reveals at least five different generations of monazite, ranging from c. 9 to >300 Ma. Petrological models of monazite chemistry provide a link between these generations and the thermal evolution of these rocks, yielding an age for the melting of Greater Himalayan rocks within the Main Central Thrust sheet (c. 16 Ma), and for the timing of thrust sheet emplacement that are younger than commonly viewed. Chemical characterization of monazite is vital prior to chronological microanalysis, and many ages previously reported for monazite from the Greater Himalayan Sequence are interpretationally ambiguous.

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Ultrahigh‐pressure metamorphic (UHPM) rocks of the Kokchetav Massif of Kazakhstan contain metamorphic microdiamond and coesite inclusions inside rigid capsules such as garnet and zircon. Precambrian protoliths of the UHPM rocks were metamorphosed at around 530 Ma, at pressures of about 7 GPa, which suggests that crustal protoliths were subducted to depths of over 200 km. Primary UHPM minerals are poorly preserved due to partial obliteration by subsequent Barrovian overprint during exhumation and later collision events in Caledonian times. We report the results of detailed mapping of the Kokchetav Massif and use structural data to propose intrusion and exhumation mechanisms for the UHPM rocks. Detailed mapping revealed that many subvertical structures in the ultrahigh‐pressure–high‐pressure (UHP–HP) units were formed due to later folding. The primary structure appears to be subhorizontal and the total thickness of the UHP rocks is estimated at around 2 km. The first order structure is sandwich‐like; that is, the UHP–HP units are separated from underlying low‐P metamorphic rocks of the Daulet Series and from feebly metamorphosed to unmetamorphosed sedimentary strata on the top by subhorizontal faults. Kinematic indicators show top‐to‐the‐south sense of shear along the top, and top‐to‐the‐north displacement along the bottom boundaries. These shear senses, together with the observed metamorphic gradients, suggest that the thin UHPM sheet was extruded toward the north. We consider wedge extrusion to have been the most effective mechanism for the exhumation of the UHPM rocks.

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